1. Field of the Invention
A method and apparatus for measuring properties of the pelvic floor muscles. More particularly, a method and apparatus for measuring a strength of the pelvic floor muscles.
2. Background of the Related Art
Approximately one-third of women over the age of 60 years suffer from stress, urinary or fecal incontinence. Approximately one in eleven women or ten (10%) percent suffer from a form of hernia called a prolapse. Pelvic muscle exercises are often prescribed as the first form of conservative treatment for such patients. In the practice of obstetrics, gynecology, urology, physical therapy and nursing, measurement of maximum voluntary pelvic muscle strength is considered a necessary measurement to assess pelvic floor muscle impairment.
Measurement of maximum voluntary pelvic muscle strength is traditionally made by an examiner using one of two methods. In the simplest technique, the examiner subjectively rates the strength of the muscle from the maximum pressure she perceives to be exerted on her two fingers by the levator muscle during a vaginal examination. See, for example, A. M. Worth et al., xe2x80x9cDevelopment and Resting of the Circumvaginal Muscles Rating Scale,xe2x80x9d Nurs. Res. Vol. 35, pp. 166-8, 1986 and C. Brink et al., xe2x80x9cA Digital Test for Pelvic Muscle Strength in Older Women With Urinary Incontinence,xe2x80x9d Nurs. Res., Vol. 38, pp. 196-9, 1989.
In a more advanced technique, measurement of pressure within a balloon device or pressure-making catheter inserted into the vagina or rectum is used to estimate pelvic muscle strength. See, for example, M. C. Dougherty et al., xe2x80x9cDevelopment of Testing of an Instrument to Access the Dynamic Characteristics of the Circumvaginal Musculature,xe2x80x9d Nurs. Res., Vol. 35, pp. 202-206, 1986 and M. C. Dougherty et al., xe2x80x9cVariation in Intravaginal Pressure Measurement,xe2x80x9d Nurs. Res., Vol. 40, pp. 282-5, 1991.
The drawback of the first method is that it is subjective. The drawback of the second method is that it is prone to artefacts including intraabdominal pressure increase, non-isometric test conditions, or passive tissue forces acting on the devices. Neither method measures the contractile force developed by the levator ani under isometric conditions in a known direction.
Indirect measure of pelvic muscle strength is currently made by measuring the myoelectric activity purportedly emanating from the levator ani muscles using surface and intravaginal electrodes or by intravaginal pressure. However, this is not a direct measurement of force developed by the levator ani muscles. Further, the small volume of the levator ani and large volumes of the adjacent thigh muscles make it likely that myoelectric cross-talk from neighboring striated muscles, as well as any muscle fatigue, renders any myoelectric estimates of levator ani xe2x80x9cstrengthxe2x80x9d unreliable. See, for example, U. M. Peschers et al., xe2x80x9cEvaluation of Levator Ani Muscle Strength-Comparison of Four Techniques,xe2x80x9d Paper #99, 1998 Int""l Continence Society, Jerusalem, Israel. Likewise, despite its current popularity, for reasons given below, intravaginal pressure is an unreliable method for measuring levator ani strength.
Further, none of the prior art devices allows correction for the mechanical effect of raised intraabdominal pressure (IAP) applied to the measurement device, via tissue-blade contact stresses developed by intraabdominal contents.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
A further object of the invention is to provide a method and apparatus capable of providing an objective and accurate quantification of the maximum volitional isometric strength of the pelvic floor muscles in healthy women with temporary neuromuscular damage following childbirth, or other trauma, and women who have fascial detachments of the levator ani. A method and apparatus are provided according to the invention for measuring the maximum isometric voluntary contractile force or strength that can be developed by a patient, the maximum rate of development of that isometric force, and the isometric endurance of the levator ani muscle. That is, pelvic floor muscle contraction force measurements may be made under controlled isometric test conditions. Moreover, the apparatus and method according to the invention may compensate for the effect of changes in intraabdominal pressure on the pelvic floor muscle.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.